PostgreSQL服务端开发学习 -- Datum

sizeof(Datum) ==sizeof(void*) ==4or8

typedefuintptr_tDatum;

typedefstructNullableDatum{
#define FIELDNO_NULLABLE_DATUM_DATUM 0Datumvalue;
#define FIELDNO_NULLABLE_DATUM_ISNULL 1boolisnull;
/* due to alignment padding this could be used for flags for free */} NullableDatum;

staticinlineboolDatumGetBool(DatumX)
{
return (X!=0);
}

staticinlineDatumBoolGetDatum(boolX)
{
return (Datum) (X?1 : 0);
}

staticinlinecharDatumGetChar(DatumX)
{
return (char) X;
}

/** CharGetDatum*      Returns datum representation for a character.*/staticinlineDatumCharGetDatum(charX)
{
return (Datum) X;
}

/** Int8GetDatum*      Returns datum representation for an 8-bit integer.*/staticinlineDatumInt8GetDatum(int8X)
{
return (Datum) X;
}

/** DatumGetUInt8*      Returns 8-bit unsigned integer value of a datum.*/staticinlineuint8DatumGetUInt8(DatumX)
{
return (uint8) X;
}

/** UInt8GetDatum*      Returns datum representation for an 8-bit unsigned integer.*/staticinlineDatumUInt8GetDatum(uint8X)
{
return (Datum) X;
}

/** DatumGetInt16*      Returns 16-bit integer value of a datum.*/staticinlineint16DatumGetInt16(DatumX)
{
return (int16) X;
}

/** Int16GetDatum*      Returns datum representation for a 16-bit integer.*/staticinlineDatumInt16GetDatum(int16X)
{
return (Datum) X;
}

/** DatumGetUInt16*      Returns 16-bit unsigned integer value of a datum.*/staticinlineuint16DatumGetUInt16(DatumX)
{
return (uint16) X;
}

/** UInt16GetDatum*      Returns datum representation for a 16-bit unsigned integer.*/staticinlineDatumUInt16GetDatum(uint16X)
{
return (Datum) X;
}

/** DatumGetInt32*      Returns 32-bit integer value of a datum.*/staticinlineint32DatumGetInt32(DatumX)
{
return (int32) X;
}

/** Int32GetDatum*      Returns datum representation for a 32-bit integer.*/staticinlineDatumInt32GetDatum(int32X)
{
return (Datum) X;
}

/** DatumGetUInt32*      Returns 32-bit unsigned integer value of a datum.*/staticinlineuint32DatumGetUInt32(DatumX)
{
return (uint32) X;
}

/** UInt32GetDatum*      Returns datum representation for a 32-bit unsigned integer.*/staticinlineDatumUInt32GetDatum(uint32X)
{
return (Datum) X;
}

/** DatumGetObjectId*      Returns object identifier value of a datum.*/staticinlineOidDatumGetObjectId(DatumX)
{
return (Oid) X;
}

/** ObjectIdGetDatum*      Returns datum representation for an object identifier.*/staticinlineDatumObjectIdGetDatum(OidX)
{
return (Datum) X;
}

/** DatumGetTransactionId*      Returns transaction identifier value of a datum.*/staticinlineTransactionIdDatumGetTransactionId(DatumX)
{
return (TransactionId) X;
}

/** TransactionIdGetDatum*      Returns datum representation for a transaction identifier.*/staticinlineDatumTransactionIdGetDatum(TransactionIdX)
{
return (Datum) X;
}

/** MultiXactIdGetDatum*      Returns datum representation for a multixact identifier.*/staticinlineDatumMultiXactIdGetDatum(MultiXactIdX)
{
return (Datum) X;
}

/** DatumGetCommandId*      Returns command identifier value of a datum.*/staticinlineCommandIdDatumGetCommandId(DatumX)
{
return (CommandId) X;
}

/** CommandIdGetDatum*      Returns datum representation for a command identifier.*/staticinlineDatumCommandIdGetDatum(CommandIdX)
{
return (Datum) X;
}

/** DatumGetPointer*      Returns pointer value of a datum.*/staticinlinePointerDatumGetPointer(DatumX)
{
return (Pointer) X;
}

/** PointerGetDatum*      Returns datum representation for a pointer.*/staticinlineDatumPointerGetDatum(constvoid*X)
{
return (Datum) X;
}

/** DatumGetCString*      Returns C string (null-terminated string) value of a datum.** Note: C string is not a full-fledged Postgres type at present,* but type input functions use this conversion for their inputs.*/staticinlinechar*DatumGetCString(DatumX)
{
return (char*) DatumGetPointer(X);
}

/** CStringGetDatum*      Returns datum representation for a C string (null-terminated string).** Note: C string is not a full-fledged Postgres type at present,* but type output functions use this conversion for their outputs.* Note: CString is pass-by-reference; caller must ensure the pointed-to* value has adequate lifetime.*/staticinlineDatumCStringGetDatum(constchar*X)
{
returnPointerGetDatum(X);
}

/** DatumGetName*      Returns name value of a datum.*/staticinlineNameDatumGetName(DatumX)
{
return (Name) DatumGetPointer(X);
}

/** NameGetDatum*      Returns datum representation for a name.** Note: Name is pass-by-reference; caller must ensure the pointed-to* value has adequate lifetime.*/staticinlineDatumNameGetDatum(constNameData*X)
{
returnCStringGetDatum(NameStr(*X));
}

/** DatumGetInt64*      Returns 64-bit integer value of a datum.** Note: this function hides whether int64 is pass by value or by reference.*/staticinlineint64DatumGetInt64(DatumX)
{
#ifdef USE_FLOAT8_BYVALreturn (int64) X;
#elsereturn*((int64*) DatumGetPointer(X));
#endif}

/** Int64GetDatum*      Returns datum representation for a 64-bit integer.** Note: if int64 is pass by reference, this function returns a reference* to palloc'd space.*/#ifdef USE_FLOAT8_BYVALstaticinlineDatumInt64GetDatum(int64X)
{
return (Datum) X;
}
#elseexternDatumInt64GetDatum(int64X);
#endif

/** DatumGetUInt64*      Returns 64-bit unsigned integer value of a datum.** Note: this function hides whether int64 is pass by value or by reference.*/staticinlineuint64DatumGetUInt64(DatumX)
{
#ifdef USE_FLOAT8_BYVALreturn (uint64) X;
#elsereturn*((uint64*) DatumGetPointer(X));
#endif}

/** UInt64GetDatum*      Returns datum representation for a 64-bit unsigned integer.** Note: if int64 is pass by reference, this function returns a reference* to palloc'd space.*/staticinlineDatumUInt64GetDatum(uint64X)
{
#ifdef USE_FLOAT8_BYVALreturn (Datum) X;
#elsereturnInt64GetDatum((int64) X);
#endif}

/** Float <-> Datum conversions** These have to be implemented as inline functions rather than macros, when* passing by value, because many machines pass int and float function* parameters/results differently; so we need to play weird games with unions.*//** DatumGetFloat4*      Returns 4-byte floating point value of a datum.*/staticinlinefloat4DatumGetFloat4(DatumX)
{
union    {
int32value;
float4retval;
    } myunion;
myunion.value=DatumGetInt32(X);
returnmyunion.retval;
}

/** Float4GetDatum*      Returns datum representation for a 4-byte floating point number.*/staticinlineDatumFloat4GetDatum(float4X)
{
union    {
float4value;
int32retval;
    } myunion;
myunion.value=X;
returnInt32GetDatum(myunion.retval);
}

/** DatumGetFloat8*      Returns 8-byte floating point value of a datum.** Note: this function hides whether float8 is pass by value or by reference.*/staticinlinefloat8DatumGetFloat8(DatumX)
{
#ifdef USE_FLOAT8_BYVALunion    {
int64value;
float8retval;
    } myunion;
myunion.value=DatumGetInt64(X);
returnmyunion.retval;
#elsereturn*((float8*) DatumGetPointer(X));
#endif}

/** Float8GetDatum*      Returns datum representation for an 8-byte floating point number.** Note: if float8 is pass by reference, this function returns a reference* to palloc'd space.*/#ifdef USE_FLOAT8_BYVALstaticinlineDatumFloat8GetDatum(float8X)
{
union    {
float8value;
int64retval;
    } myunion;
myunion.value=X;
returnInt64GetDatum(myunion.retval);
}
#elseexternDatumFloat8GetDatum(float8X);
#endif